1. Field of the Invention
The present invention is related to electrical connectors, and more particularly is directed towards a new and improved telephone-type modular jack for directly coupling a standard, telephone-type modular plug to a printed circuit board.
2. Description of the Related Art
Electrical connectors known as modular plugs and modular jacks have recently come into widespread use in the telecommunications industry. Modular plugs and modular jacks are also widely used as general interconnect devices for a variety of types of electrical equipment. As utilized herein, the terms "modular jack" and "modular plug" connote the miniature, interchangeable, quick-connect-and-disconnect jacks and plugs developed by Western Electric Company and Bell Telephone Laboratories originally for use with telephone equipment. See, for example, U.S. Pat. Nos. 3,699,498; 3,850,497; and 3,860,316. The word "modular" came to be used with these types of plugs and jacks not because the plugs and jacks themselves were modular (in the normal sense of the word), but because they modularized the telephone equipment (handsets, desksets, cord assemblies, mounting plates, etc.) with which they were utilized, i.e. these plugs and jacks enabled the telephone equipment to be manufactured in a standardized size and design to permit interchangeability of components and custom arrangements.
Several modular jacks have been proposed for directly coupling a modular plug to a printed circuit board. See, for example, U.S. Pat. No. 4,210,376, as well as each of my prior U.S. patent applications referenced above.
In my prior U.S. application Ser. No. 120,846, now abandoned, there is described a novel modular jack particularly designed to serve as a direct interface between a standard, telephone-type modular plug and a printed circuit board. This connector jack includes a plurality of conductors formed in the connector housing. One end of the conductors extend from the rear portion of the housing in an alternating, staggered fashion so as to be easily inserted into correspondingly-spaced apertures in a printed circuit board. The extending end portions form solder posts for permitting subsequent wave-soldering to pads preformed on the printed circuit board. The remaining portions of the conductors extend through the body of the housing to the front portion thereof and are then bent rearwardly into a plug-receiving opening so as to form spring contact portions which are laterally spaced so as to correspond with the contact terminal spacing of the mating, modular plug. An important feature of the modular jack of this prior application is the provision of differential spacing between the spring contact portions of the conductors and the solder post portions of the conductors. Such differential spacing permits mating of the spring contact portions with standard modular plugs, and also permits attachment of the solder posts to CAD (computer-aided-design)-generated printed circuit boards. More particularly, and by way of example, the latter requires adjacent solder posts to be spaced 0.050 inch apart, while the Federal Communications Commission requires 0.040 inch spring contact portion spacing.
In my prior application Ser. No. 215,054, now U.S. Pat. No. 4,457,570 there is described an improved modular jack that also incorporates differential spacing. The principal feature of this improved modular jack is the provision of conductors which enter the plug-receiving cavity of the jack from the rear of the jack, rather than from the front of the jack as with previous designs. This feature results in substantial economies as a result of the reduction in required conductor length, gold plating, and the like.
While an improvement over my prior and other existing modular jack designs, the device of Ser. No. 215,054 nevertheless suffers from several deficiencies. For one thing, the particular design requires the conductors to be formed in place after insertion in the housing. This has proven to be an unduly expensive and difficult manufacturing step. In addition, ultrasonic welding is required in order to maintain the conductors in place in the housing. Ultrasonic welding, while generally effective, has not proven to be as reliable or trouble-free as might otherwise be achieved with a different design.
In addition to the foregoing, there are several problems which are indigenous to most if not all modular jacks presently on the market. One problem arises when a smaller modular plug is accidentally inserted into a larger modular jack. For example, it is physically possible, given the standard dimensions of modular plugs and jacks, to place a four or six terminal plug into an eight wire jack. Since the spring contact portions of the conductors of the jack are lined up in a horizontal row in the plug-receiving opening, what occurs when this happens is that the plastic shoulders of the smaller plug strike the outer spring contact portions of the jack. This can cause the outer spring contact portions of the jack to become overstressed, resulting in permanent damage to the jack, or requiring replacement of the jack. One solution previously proposed was to incorporate plastic lock out keys or studs in the plug-receiving opening of the jack to prevent smaller plugs from being inserted. However, it was discovered that such an arrangement still permitted the plugs to be physically forced past the keys without too much effort, thereby defeating their purpose.
Another problem common to presently known modular jacks is that the design of the spring contact portions provide only a small area of contact with the conductor terminals of the male. Presently marketed jack designs all utilize a linear, diagonally extending spring contact portion which makes contact with the crown, or radiused end, of the contact terminal of the plug. This results in essentially a point of contact approximately 0.0008 inch in diameter. Several problems arise from this configuration. For one thing, when the conductors are carrying high frequency signals (e.g., 20-40 MHz), some information can be lost due to the small area of contact (i.e., signal transfer area) between the male and female conductors.
Another problem with the generally diagonal spring contact configuration is that it does not provide a uniform contact resistance as the plug is inserted and withdrawn into and from the jack. This results from the fact that the spring contact portions have a longitudinal force vector which increases and thus creates more resistance to longitudinal movement of the plug as the plug is inserted more deeply into the plug-receiving opening of the jack. Conversely, the contact resistance lessens as the plug is withdrawn from the cavity.
A further problem with the known configuration results from the fact that only a single point or area of contact is established between the female spring contact portion and the male contact terminal. If the connectors are utilized in an environment which is subject to vibration as frequently occurs, electrical continuity may be intermittently and undesirably broken.
A further problem with known modular jack designs is that they for the most part require conductors of unequal length. It would be more desirable from a manufacturing standpoint if conductors of substantially equal length could be utilized.